Logical Pluralism: Correct Logics and the Problem of Disagreement

• Applicant: Dr. Erik Stei
• Subject Area: Theoretical Philosophy
• Term: from 2016 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 317332790

Logical pluralism is the thesis that there are at least two opposing, but equally correct, logical systems. It is directly opposed to logical monism, according to which there is only one correct logic, and to Logical Nihilism-the view that there is no correct logic at all. In general, logical pluralism is motivated by the fact that there is a plurality of different logical systems. More specific versions result from different views on the correctness of a logic and on how logical systems can disagree with one another. The research project is concerned with both aspects. Its aim is to investigate whether a plausible and stable version of logical pluralism can be formulated. The first goal of the project is to find workable criteria for the "correctness" of logic. A widespread view is that those criteria concern the application of a logic to a specific subject area. There is less agreement, however, on what kinds of subject areas are to be considered. Apart from intuitively valid arguments or natural language arguments, one might resort to norms of reasoning or to metaphysically strong assumptions like logical Platonism. The plausibility of logical pluralism at least partly depends on its compatibility with different proposals. The aim is to clarify this issue. The problem of disagreement will be discussed in connection with a classical position in the philosophy of logic. W.V.O. Quine's "meaning-variance thesis" claims that a change of logic is a change of subject. More specifically, the view is that the meaning of the logical constants depends on the logical principles of the system containing those constants. The thesis is immediately relevant for pluralism: If the meaning of the constants varies with different logical systems, then it is not obvious that the systems disagree. A controversial statement like, for instance, "p or not-p" could simply mean different things. In the research project, I will connect the discussion of the meaning variance thesis to the current debate on disagreement in the philosophy of language. It is to be expected that this will lead to insights valuable to the discussion of logical pluralism. Both characteristic features of logical pluralism-the correctness and the disagreement of different logical systems-are in need of further clarification. It is the goal of the proposed research project to contribute to that task.

• DFG Programme: Research Fellowships
• International Connection: USA
• Hosts: Professor Dr. Graham Priest; Professorin Dr. Gillian Russell